Various embodiments of such installations are known in the art. Depending upon the raw materials processed in the kiln installation and/or the fuels used in the kiln installation, the exhaust gases coming from the raw meal preheater contain a more or less large proportion of SO.sub.2. Since the filter arrangements which are generally downstream of the raw meal preheater in the gas flow direction and are, for example, constructed as electrostatic filters, are not normally suitable in order sufficiently to reduce the discharge of SO.sub.2 into the atmosphere, it is also known for example to pass exhaust gases from the preheater through the raw-grinding mill of the raw material grinding installation in order to absorb SO.sub.2 fractions from the cement raw meal. However, the absorption effect of SO.sub.2 on the cement raw meal has frequently proved to be too low.
It is also known from DE-A-36 43 143 for harmful substances such as sulphur, chlorine and fluorine to be removed from the exhaust gases from a cement production plant by bringing the exhaust gases from the preheater into contact in a reaction zone with raw meal, partially deacidified raw meal and/or with partially deacidified slaked raw meal in order to fix them thoroughly therein. The solid material contained in the gas stream is then removed from the gas in a precipitation zone downstream of the reaction zone.
The object of the invention is to provide a method for removing SO.sub.2 from kiln exhaust gases and which is distinguished--by comparison with the known methods--by the use of relatively simple measures in terms of apparatus by a markedly improved precipitation of sulphur dioxide (SO.sub.2) and optionally other similar harmful substances out of the exhaust gases from the said kiln installation.